Selective signaling system



May 29, 1934. H. E. HERSHEY SELECTIVE SIGNALING SYSTEM Filed June` 29, 1928 F by the selector at the end of the Patented May 29, 1934 VSELECTIVE SIGNALING SYSTEM Harry E. Hershey, Oak Park, Ill.,

assigner, by

mesne assignments, te Associated Electric Laboratories, inc., Delaware Chicago, Ill., a corporation of Application June 29, 192s, serial Ne. 289,296

6 Claims.

This invention relates in general to selective signaling systems, more particularly to such systems in which a plurality of selectors are actur ated by impulses of alternating current, and the principal object of the invention, briefly stated, is the production oi a new and improved sender for selective signaling systems, the improvements making the sender more flexible and more reliable in its operation.

Selective signaling systems of the type disclosed in this invention have been devised heretofore, and employed in train dispatching systems, systems of remote control and power switching devices, and for many other uses, These systems may be divided into two classes, the 27th step code system, and the 17th step code system. These classications are derived from a number oi steps that the selector switches must take from their normal position to reach a ringing contact.

In the seventeen step code system, the selector switches are so arranged that in addition to ringing stations in their seventeenth positions, the

same selector may also ring a station in its nine- Y teenth position, its twenty-rst position, and its twenty-third position. Each of the selector switches is therefore capable of selecting and signaling one of the four stations available to it.

In the systems of this type devised heretofore, it has been customary to employ a key sender for each station to be called, that key being usualiy of the type disclosed in Patent No. 1,155,649, issued to G. Brown on October 5, 1915. In connection with the keys the selecting devices usually used are the selecting switches of the type shown in the Patent No. 1,206,095, issued to Joseph C. Field on October 3, 1916.

In my co-pending application, Serial No. 236,301, led November 28, 1927, I include an improved sender, to replace theindividual keys that have been used heretofore. The present invention discloses an improved modification of that sender, the improvements adding exibility to the operation of the sender.

In a seventeen digit code system, the bell rung seventeenth step is commonly known as the A position bell, the nineteenth step as the B position, the twenty-iirst step as the C position, and the twenty-third step the D position. In the normal operation of the system, employing sender oi my invention, the operation of a station selecting key will cause the selector to select the A position and ring the cell corresponding thereto. Ii the dispatcher desires to communicate with one of tions at that station, that is the B, C, or D posivswitch is controlled to select the other position, in addition to throwing the station selecting key, he must also throw a position selecting key, which will cause the sender to transmit the number of switch in the position corresponding to that particular bell.

In the systems devised heretofore, employing the Brown key mentioned above, one of these keys must be provided for each of the four positions selectable by each selector. Thus if there are sixty selectors on the line, each having four positions, a total of 240 keys must be provided in order that the dispatcr er may call any one of the stations available to him. In the present invention, I have simplified the sending arrangement so that a station key is provided for each of the selectors on the line, that is if there are sixty selectors on the line there would be sixty station keys, and in addition I have provided three keys through which the dispatcher can call the B, C, or D positions of any of the stations of the line. To call a particular D station for example, the dispatcher operates the impulses required to position the selecting A station key corresponding thereto, and the D position key, whereupon the sender transmits the correct number of impulses to ring the bell at the desired station.

y .As a further object of my invention I provide a simplified sender employing a key for each f selector on the line and three position selecting keys through the operation of which the selector any desired station available to it.

In a system employing the Brown key menl tioned heretofore, when the selector is positioned upon the contacts of a desired station, the bell thereat is rung for a brief interval, and then the selectors are released to their normal position. The dispatcher has no way oi lengthening or shortening this interval tion bell is rung. In certain instances it may be advantageous to prolong the ringing of the station bell, and accordingly as a further object of my invention, I have provided a stop key, through the operation of which the sender and selector switches are stopped after the selection has been made, and the call bell at the selecting station is rung continuously until the dispatcher releases the stop key.

In many instances, after conversing with the party at the A position oi a way station, the dispatcher may desire to converse with other parties represented by the B, C, and D positions of that way station. toiore, it would be necessary for him to operate during which the sta- 5 In systems devised herev another Brown key, to reoperate the entire system again to select the B position. In the present system, as a further object of my invention I have provided an advance key, which in conjunction with the stop key, controls the sender so that after the dispatcher has selected the A position at a particular way station, he may opcrate the advance key and advance the selector to the B position, and if desired by further operation of the advance key ring the C and D positions at that way station.

In case of emergency, the dispatcher may desire to call all of the way stations available to him. To accomplish this, as a further object of my invention, I provide a universal call key, through the operation of which the dispatcher may call all of the A, B, C, or D positions on the line.

Further objects, not speciiically mentioned here, will be apparent from a reading of the detailed description and claims which follow.

The drawing shows by the usual circuit symbols, suicient apparatus to enable a clear understanding of myk invention. In the upper left hand corner, is the way station 100, comprising the station selector which is assumed to be of the type shown in the above mentioned Field patent. This selector has access to four call bells, one from each of its A, B, C, and D positions. Connecting the way station to the dispatchers station is the line comprising conductors L1 and L2, which line is energized from the battery 93 through the impedances 90 and 91 and the springs 65 and 66 of the relay 19. This relay 19 is assumed to be an existing relay in a train dispatching system, the battery 94 is a local battery for energizing that relay. This battery is separate from the other battery used in the system, because existing relays such as 19 are built to operate on a different voltage than that employed by the sender of my invention.

' AIn the upper right hand corner of the figure I show the impulse generator 20, which is constantly operating, to generate impulses which are broken up into codes by the sender. The sender comprises the switch S including the magnet 21 and the wipers and 73, inclusive, and the control relays 1 .to 18, inclusive, through which the sender is controlled. Associated with the sender are the cross-connecting terminal blocks A, B, C, and D, the two formery containing a sufficient number of pins to permit ready connection to the banks over which wipers 72 and 73 rotate. Since the switch mechanism S is assumed to be a4 switch of the type oi the well known rotary line switch, whose wipers move in one direction only and when the magnet deenergizes, the terminal blocks A and B will each have twenty-five contacts, one for each contact in the bank ci the switch S. Terminal blocks C and D will be equipped with the same number of contacts as there are stations selectable by the sender, that is, there is a Contact for each station in each of the C and D terminal blocks.

Associated with the sender are the station keys X and Y each with its individual relay, through the operation of which the sender is arranged to send a particular code corresponding to that station. When the key `X is pressed, for example, the relay 13 energizes and locks itself energized and arranges the sender to transmit a particular code 7-7--3. yI have also provided a universal call key and. an advance key, through Ythe operation of which particular functioningot the sender can be accomplished. The B, C, and D position keys and their associated relays 15 to 17, inclusive, are shown in the lower right hand corner or" the drawing, and through the operation of these keys the corresponding points at the way station can be selected. The stop key is shown in the lower left hand corner oi the drawing.

In order to avoid unnecessary complications of the drawing, I have used the symbols of a plus sign within a circle and a minus sign within a circle to designate the positive and negative terminals oi the battery.

Assume that the dispatcher desires to ring the bell at the A position of station 1GO and that the code of that station is 7-7-3. To call this station, the dispatcher operates the station key X, thereby closing a circuit from positive battery through springs 50, common conductor 79, through the key X, through the winding of relay 13 to negative battery. Relay 13 pulls up over this circuit and locks itself through springs 53 and conductor 76 to positive battery through the normally closed contacts controlled by springs 47. The energization of relay 13 at springs 54 and 55 connects positive potential to the contacts Cl in the terminal block C and D1 in the terminal.

block D, these terminals being` connected through jumpers to the pins A7 and B13 respectively, for a purpose' which will be apparent hereinafter. Relay 13 at springs 52 closes a circuit from positive battery over conductor 7 8, springs 48, through the normal position and wiper 71 of the switch S, through the winding of relay 12 tonegative battery, energizing the relay 12. Relay 12 at springs 50, opens the circuit over which relay 13 was energized by removing positive battery from conductor 79, thereby rendering the station keys and the universal call key ineffective should any of them be inadvertently pressed before the completion of the present call.

The energization of relay 12 substitutes the magnet 21 for the resistance 95 in the circuit over which the common interrupter 20 is operated, thereby completing a circuit from negative battery through spring 49 and its make contact, the winding of magnet 21, through the winding of the interrupter 20 to positive battery. The interrupter 20 energizes over this circuit but because of the high resistance of the winding 20, marginal stepping magnet 21 does not energize. When the interrupter 2O closes springs 62, it applies direct positive battery to the terminal of magnet 21 and that magnet energizes preparatory to advancing the wipers 70 to 73 of the switch S one step. The operation of the spring 62 short circuits the winding 20, permitting the interrupter to deenergize, at the end of which deenergisation the springs 62 are again opened. The operation of spring 62 also closes the circuit through the cut-orf key CO and the lamp 8l to negative battery, to light that lamp to apprise the dispatcher that impulsing is in progress. When the springs 62 are opened, the lamp is energized through the high resistance of the winding 20, which resistance is suiiicient to prevent the lamp from being lighted.

The energization of magnet 2l operates springs 46. and 51 without particular effect at this time. When the magnet deenergizes, the wipers 70 to 73 are advanced one step, thereby closing a locking circuit for the relay 12 traceable from positive battery through the winding of relay 11, through Vthe multipled contacts of the bank over which wiper 71 passes, the rst contact of that bank now engaged bywiper 71, through the Winding of the start relay 12 to battery. Relay 11 energizes over this circuit and relay 12 is maintained energized. The energization of relay 11, at springs 47 removes direct positive battery from the locking conductor 76 and substitutes therefor the locking battery through the winding of relay 11 and the wiper 71, for a purpose which will be apparent hereinafter. At springs 48, relay 11 opens a point in the common start conductor 78, to prevent a further placing of positive battery on the normal position engaged by wiper 71, to thereby insure that the switch S will stop when its normal position is reached. No other circuit changes are effected responsive to the rst step taken by the switch S, nor are there any changes made until the switch has taken four steps to bring the wiper into engagement with its fourth bank contact.

Referring now to the energization oi the start relay, at springs 50, it closes a circuit from positive battery through the conductor 77, through the winding of relay 18 to negative battery. Relay 18 energizes over this circuit and at spring 67 prepares a point of the local circuit of the reversing relay 19, which circuit is held open at springs 30 of the impulse relay at this time.

When the wiper 70 engages its fourth bank contact, a circuit is closed from positive battery through springs 34, conductor 74, the fourth bank contact engaged by wiper 70 and that wiper, springs 51, springs 43, conductor 75, springs 3l, through the winding of the impulse relay l to negative battery, energizing that relay. The energization of relay l, at springs 30 completes the circuit for relay 19 which energizes and at springs 65 and 66 reverses the connection between the battery 93 and the lines L1 and L2. This transmits an impulse over the line, to operate the magnet 96 of the selector 100, and similar magnets of each of the other selectors on the line. The selectors take one step. When the magnet 2l again energizes preparatory to advancing the switch S another step, the circuit or" relay 1 is opened at springs 51, and that relay falls back to open the circuit of relay 19 at springs 30. Relay 19 upon falling back, again reverses the polarity of the battery 93 with respect to the lines L1 and L2, to transmit anotherimpulse to operate the magnet 96 and other similar magnets connected to the line. When the magnet 21 falls back, switch S is advanced another step, and the circuit of relay 1 closed again to again close the circuit of relay 19.

This operation continues until the wiper 72 engages its seventh bank contact, at which time seven impulses have been transmitted over the line Ill-L2, and the arm 101 of the selector 100 is in its seventh position. Responsive to the positio-ning of the wipers 72 upon the Contact 7, a circuit is closed from positive battery through springs 54, terminal block Cl which is jumpered to terminal block A7, the seventh bank Contact and wiper 72, through the winding of relay 9 to negative battery. Relay 9 energizes over this circuit, locks itself at springs 42 to positive bat- 'tery through springs 39, thereby maintaining itself energized independently of the wiper 72. At springs 49, relay 9 places positive battery on conductor to maintain the relay 1 vent-:rgiaed independently of the magnet 2l. Relay 19 therefore is held energized and the magnets 96 and other magnets on the trunk remain inert since one polarity of battery is maintained on line L1--L2. Responsive to the transmission of the digit 7, all of the magnets of the selecting switches have stepped their respective wipers to the seventh position. 1n this position, switch and other switches whose first call digit is 7, come to rest and stay in that position because the spring 162 engages a pin, not shown, to maintain the wiper advanced. Those selectors whose switches are not arranged to respond to the digit 7 return to their normal positions. Because the return to normal of the switch requires an appreciable length of time, a delay circuit is introduced so that the switch S takes two steps before any further impulses are delivered to the impulsing relay l. v

The energization of relay 9 at springs 41 prepares a circuit which is closed when the magnet 21 is energized, which circuit is traceable through springs 46 and 36, through the winding of relay 5 to negative battery. Relay 5 energizes over this circuit and at springs 35 prepares a locking circuit or itself and ther relay 6. The relay 6 does not energize this time, since it is short circuited, by having positive battery placed upon the Lipper terminal through springs 35, and positive battery placed en its lower terminal through springs 39. When the magnet 21 deenergizes, to advance the wipers of the switch another step, the short circuit is removed fJorn` relay 5, that relay energizes, in series with the relay 5, holding the relay 5 energized. At springs 36, relay G transfers the initial energizing circuit of relay 5 to the relay 7. When magnet 21 again energizes and springs Li6 are closed, relay 7 energizes over a circuit from positive battery through springs 41, springs 46, springs 36 and its make contact, springs 33, through the winding of relay 7 to negative battery. Relay 7 upon energizing prepares a locking circuit ioritself and relay 8 at springs 37. The relay 8 being short circuited does not energize until the magnet 21 falls back.

When relay 8 energizes, springs 39 open the locking circuit of the relay 9, and relays 5 and 6. Relay 9 falls back, to again place the circuit of relay 1 under the control of the motor magnet 21, and impulsing is resumed. During the interval that the relay 9 was locked up, two impulses were transmitted by the magnet 21 to move the wipers Yover two bank contacts into engagement with their respective ninth bank contacts. Responsive to the deenergization of relay 9, relays 7 and 8 are unlocked and restore to normal.

Upon the resumption of impulsing, seven impulses are transmitted over the line before any further circuit changes take place. Simultaneous with the transmission of the seventh impulse,

wiper 73 is moved into engagement with its thirteenth bank contact, and a circuit is completed from positive battery through springs 55, terminal block D1 which is jumperecl through terminal block B13, thirteenth bank contact and wiper 73, through the winding of relay 10 to negative battery. Relay 16 energizes over this circuit, locks itself energized through springs 45 and springs 39. At springs 44, relay 10 prepares a circuit which is closed when the magnet 21 is again energized, which circuit extends through the winding of relay 5. At springs 43, relay 10 opens a point in Vthe circuit of relay 1 to remove that relay from the control of the motor magnet 21. With the relay 1 deenergized, relay 19 falls back andthe magnet 96 and other magnets of the selector switches on the trunk are maintained at one polarity. Those switches whose second digit is seven are maintained in their operative position by the interaction oi the pin and spring 102 and the remaining switches restore to their normal positions. As before, the switch S is stepped over two bank contacts, before the impulsing is resumed, the relays 5 to 8, inclusive, act ing as hereinbefore described to absorb two impulses and to nally unlock the relay 10.

When impulsing is resumed, the last digit of the code is transmitted, three impulses being delivered over the line by the alternate energization and deenergization of the relay 19. When the second impulse is transmitted, the wiper 72 is brought into engagement with its sixteenth bank contact, to complete a circuit from positive battery on spring 59, the sixteenth bank contact and wiper 72, through the relay 9 to negative battery, to energize the relay 9. The energization of relay 9 closes at springs 40 the circuit of relay 1, to energize that relay, to close the circuit of relay 19 to transmit the last impulse of the series. Relays 1 and 19 are maintained energized as long as the wiper 72 engages positive battery and the relay 9 is thereby maintained energized, and since all of the remaining contacts in the bank over which wiper 72 passes are maintained at positive potential, those relays will be energized until the switch has stepped around into its normal position. The operation of relay 9, upon the engagement of wiper 72 with the 16th contact of its bank, at its armature 41 and make contact prepares the circuit of relay 5, which circuit is comple ted upon the next operation of the stepping magnet 21. As previously explained, relay 5 operates and locks itself in series with relay 6, which relay energizes when magnet 21 restores and opens the energizing circuit of relay 5 to prepare the energizing circuit of relay 7. Relay 7 operates upon the next operation of the magnet 2l and locks itself in series with relay 8, which relay energizes in series With relay 7 when magnet 21 restores. Relay 8 at its armature 39 opens one locking circuit for relays 5 and 6 and for relay 9. Relay 9 remains energized as long as wiper 72 encounters positive battery, so consequently relays 7 and 8 remain energized. Relays 5 and 6 also remain energized since their series circuit remains completed through armature 42 and make contact of relay 9 to positive battery, in parallel with relay 9, through wiper 72. This operation of relays 5 to 8, inclusive, is without any effect at this time.

At the substation,l responsive to the receipt of the last impulse by the magnet 96, the wiper 101 was moved into engagement with its A position contact, to thereby close the circuit from positive battery through that wiper and contact through the associated bell to negative battery, to ring the bell to call the attendant at that station to the telephone.

When the wiper 72 moves into its normal pos1- tion, the circuit of relay 9 is opened, that relay falls back to open the circuit of relay 1 which in turn falls back and opens the circuit of relay 19. The deenergization of relay 19 transmits a single impulse over the lines L1 and L2, which acts as a clearing out pulse, by operating the magnet 96, in such a manner as to restore the arm 191 of the switch to normal. This operation of the selector can best be obtained from a reading of the above mentioned Field patent. When the wiper 71 moved into engagement With its normal position contact, the circuit of relays 11 and 12 is opened, those relays restore, relay 12 restoring immediately and relay 11 after a brief interval. The restoration of relay 12 again inserts resistance 95 in series with the interrupter 20, and removes' the magnet 21 from the circuit. The deenergization of relay 12 also opens the circuit of relay 18, which relay being a slow to release relay maintains its armature 67 operated for a brief interval.

Since relay 13 is also locked in series with relay 11, it also restores to normal when wiper 71 steps to its normal position. If relay 11 were to restore before relay 13 could restore and open its locking circuit at its armature 53, the relay 13 would be maintained operated from positive battery through normally engaged contacts 47 of relay 11. Therefore, to insure the release of relay 13, relay 11 has been made slow-to-release by the provision of the copper slug upon the heelend of its core.

Assume now that the dispatcher desires to call the party represented by the B position of the selector 100. To do this he operates the station key X, to arrange the sender S to transmit the code 7-7-3 as before. In addition to this he operates the position key B. The operation of the key B energizes the relay 15. The relay 15 at springs 59 removes positive battery from the sixteenth bank contact over which wiper 72 rotates. When the Wiper 72 engages the sixteenth contact, simultaneously with the transmission of the second impulse of the digit 3, the last digit of the three digits no circuit will be completed for the relay 9 since ground has been removed from the sixteenth bank contact. Magnet 21 will again close the circuit of relay 1 to transmit the third impulse of the code, and a moment later will deenergize it to transmit a fourth impulse when the wipers are moved from the sixteenth to the seventeenth bank contact. When the wiper 72 engages its seventeenth bank contact, the circuit of relay 9 is closed, and that relay is energized to again energize the relay 1 which energizes relay 19 to transmit the fifth impulse of the series. Thus, it Will be seen that the selector switch 100 is made to take two extra steps before the magnet 19 comes to rest energized and before it comes to rest with the pin engaging spring 102. The code of the call has been altered by the operation of the key from 7-7-3 to.7-7-5, and the bell associated with the contact B of the switch 100 rung to call the proper party to the telephone.

Similarly the operation of the key C energizes the relay 16 and removes positive potential from the seventeenth bank contact over which wiper 72 rotates, and in addition energizes the relay 15 to remove positive potential from the sixteenth bank contact. In this case, responsive to the energization of the key X, the sender will be caused to send 7-7-7, the four extra impulses being inserted in the last digit of the code.

Similarly the operation of the key D closes the circuit for relay 16 which energizes and closes the circuit for relay 15 which energizes. Relays 15, 16, and 17 remove positive battery from the sixteenth, seventeenth, and eighteenth contacts engaged by wiper 72, and the code is accordingly altered to 7-7-9 to bring the wiper 101 of the switch 100 into engagement with the D position contact. i

From the foregoing it will be apparent that any one of the four bells accessible from the switch 100 can be selected and rung for an interval of time, that interval of time being that which is required for the Wipers of S to pass from their sixteenth, seventeenth, eighteenth, or nineteenth position, as the case might be, to their normal position. It may happen that the dispatcher desires to ring one of the bells for a longer interval of time, this occasion would arise if he were having trouble in ringing one of the attendants represented by the positions A, B, C, and D. The dispatcher, to call under this circumstance, would operate the locking stop key, and the station key X as before. The operation of the key X arranges the sender to send '7-7-3, and the transmission of the digits773 is accomplished in the hereinbefore explained manner. The operation oi the stop key disconnects the nineteenth bank co-ntact over which wiper 71 rotates from the remaining contacts of that bank. When the wipers of switch S engage their sixteenth bank contacts, the code 7-7-3 has been transmitted. During the time that thev switch S steps from the sixteenth to the nineteenth bank contact, the bell at the selected staion is being rung. When the nineteenth bank contact is reached, the circuit of relay 12 is opened, since the wiper 71 fails to pick up positive battery. Relay 12 falls back, removing the magnet 21 from the control of the impulsing interrupter 20. The wipers of the switch S are therefore brought to rest upon their nineteenth bank contacts. The circuit of relay 1 and consequently the circuit of relay 19 is maintained en- '.ergized by the wiper 70 resting upon its nineteenth bank contact so that the switches on the line are not released. As long as the dispatcher holds the stop key depressed, the bells at the call station will be rung. The operationV of the stop key also closes a circuit irorn positive battery through that key and the conductor '77 to the relay 18, to maintain that relay energized after the start relay l2 has deenergized.

If after an interval the dispatcher does not receive any response to his long ring, he may try to ring one of the other parties at the way station in which switch 190 is located. To do this he presses the advance key closing a circuit from positive through the winding of relay 2 to negative battery energizing the relay 2. The advance key closes a parallel circuit through relay 3 to battery. Relay 3, has a copper slug at the armature end or" its core, represented on the drawing by the shaded portion at the upper end of the core, and does not immediately energize. The energizaticn of relay 2 at springs 31 opens a point in the circuit of relay 1 permitting that relay to deenergize to thereby deenergize relay 19 to transmit an impulse over the line circuit to the selector switches. Relay 3 energizes after an interval and opens at springs 32 the circuit of relay 2. Relay 2 falls back and closes the circuit oi relay 1 which again energizes, whereupon relay 19 energizes and transmits a second impulse over the line circuit. These two impulses operate the switch 10G, and other similar switches on the trunk line, causing them to take two steps. The wiper 101 of switch 100 is thereby brought into engagement with the B position contact, and the bell associated therewith is rung. If the dispatcher does not get any response from this bell, he can again operate the advance key and the interaction of relays 2, 3, 1, and 19 will transmit two more impulses over the line to advance the Wiper 101 to its C position.

When the dispatcher restores the stop key, positive battery is replaced on the nineteenth contact engaged by wiper 71, the start relay 12 is re-energized, and the switch S stepped around into its normal position in the hereinbeiore explained manner.

In case of an emergency, it may be advantageous for the dispatcher to call all of the way stations on a line simultaneously to transmit urgent orders. The selector switches such as 100 arrive at the A position when they have taken seventeen consecutive steps. Normally these steps are divided up into a three digit code,

with suitable pins arranged to hold the desired selector in operated Vposition While the remainder release. To call all of the A position stations on the trunk, the dispatcher throws the universal call key. This closesl a circuit from positive battery to spring and its normal contact ough the universal call key, through the windof relay 4l to negative battery. Relay i en- 'gizes over this circuit, locks itself to conductor iii at springs S3. t springs 311, relay 4 removes positive battery from the fourth, fifth, and sixth contacts of the bank over which Wiper '70 rotates. The removal of this positive battery from these contacts delays the starting of the transmission oi impulses to relay 1, while four steps are taken by the switch S. The energization of relay 4 at springs 68 closes a circuit for the start relay 12 to start the sender transmitting impulses to the motor magnet 21. During the rst seven steps nothing happens and when the wiper l0 engages its eighth bank contact, the relay l is energized and impulses are transmitted over the line conductor in the hereinbefore explained manner. Since the relay 4 does not register any potentials in the C and D terminal blocks, wipers 72 and 73 do not pick up positive potential, and no pauses are inserted in the series of impulses. Seventeen impulses will be transmitted over the line without interruption, at the end or which tfme wiper 72 engages its sixteenth bank contact, relay 9 comes to rest and is energized, and relay 1 locked up in the hereinbefore described manner. Similarly at the substations each selector switch has been stepped seventeen steps to its A position contact, and the bell corresponding to that Contact is rung. When the wipers of the switch S pass into their normal position, the cir- J cuit of relay 9 is opened, and the sender is restored to normal. When relay 1 deenergizes, relay 19 falls back and sends the clearing out pulse to restore the selector.

If the dispatcher wishes to issue a general call l to the B positions he operates the B position key in addition to the Auniversal call key, and nineteen impulses are sent out without interruption. Similarly the C and D positions can be called by manipulation of the C and D position keys and the universal call key.

Throughout the drawing, I have shown a particular type of apparatus, to illustrate my invention by way of example only, as there are many modifications and adaptations which can be made by one skilled in the art without departing from the scope and spirit of the invention.

Having thus described my invention, what I consider new and desire to protect by Letters Patent is pointed out in the appended claims.

What is claimed is:

1. In an impulse transmitter, an impulsing relay, a stepping switch having a normally fixed stopping position, a plurality of keys representing different three-digit codes, an auxiliary key, means responsive to the operation of any one oi said code keys for stepping said switch and operating said relay to transmit impulses, means operated responsive to said switch reaching said stopping position for stopping the operation of said relay after a certain number of impulses have been transmitted, means controlled jointly by said switch While stepping and the operated one of said code keys for controlling the operation of said relay to arrange the impulses transmitted thereby into three groups corresponding to the three digit code represented by the operated key, and means responsive to the operation of said auxiliary key' for moving the stopping position of said switch to alter the last of said three groups by allowing said relay to transmit additional impulses.

2. In an impulse sender, an impulsing relay, a stepping switch having a normally Xed starting position, means for stepping said switch and operating said relay when said switch reaches said starting position to transmit a given number of impulses, means controlled by said switch for controlling the operation of said relay to arrange the impulses transmitted thereby into three groups and insert a pause period between the rst and second groups and between the second and third groups, said pause periods each equal to the time required for said switch to take two steps, and means for moving said starting point while said switch takes a number of steps equal to the sum of the steps taken by said switch during said pause periods to control the operation of said relay to cause it to transmit a single group of impulses equal in number to said given number.

3. In an impulse transmitter, a stepping switch having a normal position, means for stepping said switch from its normal position through a definite number of steps back to its normal position, means controlled by said switch while stepping for transmitting impulses, means for stopping said switch before it reaches said normal position, and means for thereafter controlling said impulsing means independently of said switch for transmitting additional impulses.

4. In an impulse transmitter, an impulsing relay, a stepping switch, means for stepping said switch, means whereby said relay is operated by the stepping of the switchto transmit a series of impulses, the series of impulses transmitted always consisting of the same number of impulses, means for controlling said switch to arrange the series of impulses transmitted by the relay into codes separated by pauseperiods between Vcertain successive impulses of a series while retaining the stepping action of said switch uniform irrespective of the codes being transmitted, and means for controlling the operation of the switch to arrange the seriesof impulses transmitted by the relay into a single group of impulses Without pauses; the number of impulses transmitted still being the same as the number transmitted by the relay and switch when transmitting a code.

5. In anrimpulse transmitter, a stepping switch having a normal position, means for stepping said switch from its normal position, an impulsing relay, means whereby said relay is operated by the stepping of said switch to transmit impulses after said switch has taken a denite number oi steps from its normal position, means operated by said switch in diierent positions thereof for preventing the operation of said relay by said switch while said switch is taking a plurality of said steps to insert pause periods between certain impulses to arrange the impulses into groups, and means whereby the operation of said relay by said switch is prevented until said switch has taken a number of steps from its normal position equal to said denite number plus said plurality of steps to thereby cause said relay to transmit a single group of impulses equal in number to the impulses comprising said groups.

6. In an impulse transmitter, a stepping switch, a three-digit-code key, a single-digit-code key, means rendered effective by the momentary 0peration of either of said keys for uniformly stepping said switch, a relay operated by said switch while stepping for transmitting impulses, means rendered effective by the operation of said threedigit-code key and thereafter controlled by said switch for controlling the operation of said relay to arrange the impulses transmitted thereby into a three-digit code by inserting pause periods between certain of the impulses, said last 

